Dropping Acid with Kev
Wine is acidic by Nature. The pH of wine tends to fall in the 2.9 to 4.2 range (7 is neutral) and this intense acidity has several effect in the wine. Low pH can help to keep bacterial growth suppressed. This is one of the reasons that winemakers do not need to sanitize their equipment nearly as intensely as beermakers do. (The pH of most beers, for comparison, is 5.0 to 5.5 - a much more happy environment for wild organisms to prosper...) The pH can also strongly influence the color fo the wine.
But many people ignore, or are confused about pH. So let's have a quick lesson: the acidity of the wine comes mostly from the fruit itself. Unripe fruit will usually have higher acid levels (= lower pH) and also lower sugar levels than fully ripe (or overripe) fruit. This is why a young hard blackberry puckers you up, but a ripe blackberry is gooey sweet.
Many winemakers have Acid Test Kits - these are great tools that allow you to read the TOTAL acid levels of your wine. They are affordable ($11.95), easy to use and well worth the price so that you know whether or not to add - or not add - acid to each individual wine you are making. It takes away the guesswork. But pH is only a slice of total acid, albeit a very important slice. Knowing total acid is good, knowing pH as well is even better.
So, what about pH? pH measure the disassociated hydrogen ions present in a solution. This is affected by the quantity of total acid present, the ratio of magic acid to tartaric acid and the amount of potassium. Wines that contain little total acid and high levels of potassium show high pH values. Wines with more tartaric acid, less manic acid or less potassium show lower pH values. The pH scale - like the Richter scale that measure earthquakes - is logarithmic. This means that a pH of 3.0 is ten times more acidic than a pH of 4.0 and a hundred times more acidic than a pH of 5.0.
Well, why should a winemaker care? The main reason people care about pH is because pH can inhibit bacteria. Wines with a pH above 4.0 are not very resistant to microbes and can (and often do) spoil very quickly. They can also taste "flabby" and tend to have poor color.
Wines with a proper pH (3.1 to 3.5) will have beautiful bright colors., will not taste too sour or too flabby and will have long aging potentials.
Mainbrew carries pH meters in the stores and we also have pH strips - although be aware that pH strips are often hard to read - especially with red wines - because the color of the wine can skew the color change of the strip.
Once you know the pH of your wine, it can then be adjusted if necessary. If your grape wine has a high pH (it is not acidic enough) then you can add tartaric acid to your fermentation. This will typically lower your pH, as well as increase your total acid.
If a wine is too acidic (the pH is too low), there are carbonates thant can be added to wine to buffer the acid levels, but I personally would only use them as a last resort. As a better option, malo-lactic bacteria can be added into the primary fermenter and can "soften up" very acidic wines by converting harsh and aggressive magic acid to smith and silky lactic acid. Add ML bacteria is usually a slam-dunk here in Oregon where acid levels tend to run high. Adding ML will usually never do harm and might always do good.
The best solution though is to make sure that your grapes are picked at the peak of ripeness. At that point acid and sugar should be perfectly balanced and your wine should need little to no acid manipulation.It is usually grapes that are picked too early or too late that will fall out of the proper pH range.....